The offenders leave the power lines dangerous and exposed once they get what they want, police said. On one occasion a set was left broken outside Phillip St preschool.
“Our message to offenders is to stop this behaviour before someone, including yourself, gets hurt,” said Senior Sergeant Roy Appley.
“You are putting yourselves and others at extreme risk of electrocution, for such a small return.”
Police are appealing to the public for any information that could assist in identifying those involved.
They are urging residents to ring 111 immediately if anyone is seen acting suspiciously around power poles or lines.
“If you hear anything out of the ordinary overnight, do not think nothing of it,” Appley said.
“We need Christchurch residents to be aware of the risk of exposed or damaged wires – do not touch them and call Orion on 0800 363 9898 straight away.”